Denture buildup or calculi occurs because of secretions within the mouth of the denture wearer. The parotid gland secretes material through Stenson's duct located between the first and second molars. The submandibular gland secretes additional material through Wharton's duct which is located underneath the tongue. Finally, the sublingual ducts secrete through the Rivina duct which is located on the floor of the mouth. These three glands continue to operate after the teeth have been removed. These secretions leave amylase and mucin (saliva) deposits on the dentures and cause buildup on the dentures. Of course, food particles and stains from, for example, coffee, tea and smoking also occur on dentures
In order to avoid denture buildup or otherwise rid the dentures of such buildup and stains, the dentures must be cleansed from time to time. Denture cleansing is generally carried out either by brushing dentures with a paste or by soaking dentures, typically overnight, in an aqueous cleansing solution. Aqueous denture cleanser solutions are known and generally compose tablets, granules, or powders that are dissolved in water to form a cleansing bath or cleansing system in water.
Numerous denture cleansing compositions, typically provided in tablet or powder form, are well known in the art for this purpose. Traditionally, these compositions have contained a variety of sulfate salts, such as bisulfates, monopersulfates, and sulfates as detergents, oxidizers and the like, and have also utilized alkali metal and alkaline earth metal halides as bleaches. Such compositions have also included perborate, carbonate and phosphate salts in various amounts to provide effervescence and cleaning activation.
Unfortunately, the cleansing systems produced by these compositions when dissolved in water are insufficient in many respects. It is oftentimes very difficult to remove calculi and other deposits from the dentures, and effective cleansing of the dentures continues to be an extremely difficult problem in the care of dentures.
Monopersulfates such as, for example, sodium monoperoxysulfate and potassium monoperoxysulfate are well known cleansing agents often used in denture cleansing compositions. Monopersulfates are active peroxide (oxygen) bleaches which are known to be effective cleaners of organic material and may also work as a disinfectant. However, it is understood in the art that monopersulfate, including particularly potassium peroxysulfate, is most active without other agents added. Moreover, the cleaning activity of monoperoxysulfate is also selective, being much greater for organic materials. Hence, when certain other cleansing agents are added, it is well known that the cleansing activity of the monopersulfate may be reduced and, depending upon the type and amount of the additional cleansing agent added, this may significantly affect the efficacy of the composition.
For example, sequestering agents such as polyfunctional organic acids, such as citric acid, maleic acid, fumaric acid, phosphates, phosphonates, pyrophosphates, and their corresponding salts, are known to reduce the activity of the monpersulfate compound, but increases its stability. It is known that a monopersulfate compound may be decomposed by biological materials and/or by metal ions, particularly in acid solutions. Since the monopersulfate compound forms an acid in solution, the addition of a buffer such as a salt of a polyfunctional organic acid decreases the acidity of the solution, thereby prolonging the life of the monopersulfate compound. Additionally, since these salts are known to complex with metal ions, the decomposition of the monopersulfate compound is thereby further inhibited. On the other hand, addition of these salts, when added in too large of proportions start to decompose the monopersulfate rather than protect it. Thus, the proportion of the monopersulfate compound to other active agents in the composition is oftentimes considered critical to the cleansing efficacy of the composition and must be carefully controlled.
In addition, it has become increasingly known that bacteria, fungi, and other microorganisms can grow on dentures which can cause infection and reinfection problems in the oral cavity and gums of denture wearers, particularly those in nursing homes and the elderly. Among the more notable bacteria commonly found in dentures are Candida albicans, Actinomyces viscosus, Streptococcus pyogenes, and Streptococcus mutans.
Thus, the need exists for a denture cleansing composition which is effective not only as a cleanser, but also will effectively eliminate and kill bacteria, fungi, and other microorganisms in a manner which is safe to the denture wearer.
In the art, monopersulfate-containing cleanser compositions are well known. U.S. Pat. Nos. 4,857,224 and 5,486,304 both disclose such compositions. These compositions may also include a sequestering agent which functions as an additional cleanser to the extent that it reacts with the calcium present in the calculus that accumulates on dentures during the day. However, neither of these references address the need for an antimicrobial disinfectant. U.S. Pat. No. 5,486,304 does, however, indicate that sodium benzoate can be used as a lubricant and/or compression aid in an amount ranging from about 0.1 to about 0.8 percent by weight. This minor amount of benzoate is not significant enough however to provide sufficient antimicrobial activity to the composition.